Telephone-exchange system



*June m. y1924.

H.v L41 HOFFMANN TELEPHONE EXCHANGE s'rsru Filed sept..V e.. -1919' Afgy.

Patented .lune l0, 1924.

rar

HENRY L. HOFFMANN, on sr. noms,v MIssOURI, JfissIeNOR 'To AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, a CORPORATION or NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed September To all whom t may concern.' y

Be it known that` l, HENRY L. HOFFMANN, residing at St. Louis, in the cit-y of St. Louis and State of Missouri, have invented certain Improvements in Telephone-Exchange Systems, ol? which the following is a specification.

This invention relates to telephone eX- change systems and more particularly to such systems in which Aconnections between telephone lines terminating at manual and automatic exchanges are established by way of trunk circuits, over which automatic switches are controlled from the manual eX- f change for effecting connections between the trunk circuits and Vtelephone lines at the automatic eXchange.

The Object of this invention is the production oIp an improved system of this character, by which the operators at the manual exchange may cont-rol automatic' switches provided at the automatic eX- changes andin which complete supervision over the connection is given to the operators at the manual exchange.

In accordance with the various features or this invention, an operators impulse sendingdevice provided at the manual Otli'ce and common to the link circuits thereat, is rendered individual to a link circuit when connected with a trunk circuit extending to the automatic exchange by means responsive to the initial actuation of the impulse sending device. A'li/leans provided at vthe manual oliice and controlled-over the trunk circuit in turn controls the disconnection ot the impulse sending device from the particular engaged link circuit, and Jfurther means under the control yot the operator is provided whereby, if the sending device has not been disconnected by the -means con.-v

trolled over the trunk circuit prior to the time that the operator desires to connect the sending device with another link circuit, the operaor may disconnect the sending device from the engaged link circuit. iffondensers are provided in the talking conductors of the trunk circuit which normally prevent the flow vof direct current from the manualy to the automatic eX- change, and which upon the connection of the operators sending device with the enc, rela. serial Nofeeaoea to the automatic exchange, at which are provided the usual selector and connector switches for effecting connection between the trunk circuit and telephone lines, suchv as l), terminating atl the automatic eX- change. The apparatus shown to the left of the dotted line 1,-1' is located at the manual exchange, and that to'the right thereof at the automatic exchange. The nature of this invention is such that it is believed that a clear understanding thereof will be obtained from a description of the operation ot' the system shown yin the drawing, and it will be so described.

The subscriberat telephone line A having initiated a call and the answering end of the link circuit B having been associated therewith inV any well known manner, the operator actuates listening key 5, connectingthe operators telephone set inl circuit so that the Operator may converse with the calling subscriber to ascertain the number or the line with which connection is desired. Assuming that connection is desired with telephone line D, which terminates at the automatic exchange, the operator inserts calling plug 6 of the link circuit B into jack of the trunk circuit C. Calling supervisory lamp 8 and sleeve relay 9 are thereupon operated over a circuit from battery, through the lamp 8, resistance '10, sleeve contacts oit the plug 6 and the jack 7 and the windings of relays 9 and 1l to ground. llelay ll is marginal and does not operate in series with resistance 10 and the winding of relay 9, resistance 10 being comparatively high. "he operation of relay 9 bridges polarized relay 13 across the talking conductors of the trunk circuit on the automatic exchange side of condensers 14 and 15 provided in the talking conductors for the purpose of normally preventing the flow of direct current from the manual to the automatic exchange. Polarized relay 13 does not operate at this time for the direction of How of current through its windings is such as to prevent its operation.

The opera-tor may now actuate an operators impulse sending device 2O which is common to the link circuits at this operators position. Upon the initial actuation of the impulse sending device 20, the off-normal contact 21 thereof is closed, causing the operation of sending device connecting relay 22 over a circuit from battery through the normal contact of pilot relay 23, oil-normal contact 21, lower contact of listening key 5, contact 24 and winding or' relay 22, and the contact of polarized relay 25 to ground.

Relay 22 in operating completes a locking circuit for itself from battery, through the Winding of pilot relay 23, contact ot the operator-s switching key 26, contact 27 and winding of relay 22, and the contact of polarized relay 25 to ground. The opera tion of relay 22 opens the talking conductors of the link circuit B and bridges the impulse contact of the sending device and polarized relay across the talking con-A ductors of this link circuit connected with the plug 6. The energization oit pilot relay 23, resulting from the closure of the locking circuit of relay 22, opens a contact in the original energizing circuit of relay 22 and causes pilot lamp 28 to be lighted, indicating that the sending device 20 has been rendered individual to one oi? the link circuits and connected therewith. The closure of contact 29 of relay 22 connects resistance 30 in parallel with supervisory lamp 8 and resistance 10, thereby lowering the resistance of the circuit which includes the winding of relay 11, which thereupon operates.

The operation of relay 11 opens the bridge which contains the polarized relay 13 and short-circuits the condensers 14 and 15 to provide a path tor the direct current im pulses controlled by the sending device 20. Upon the short-circuiting of these condensers impulse responsive relay operates over a circuit from ground through the right-hand winding of impulse responsive relay 35, right-hand normal Contact of reversing relay 36, upper alternate contact oi relay 11, tip contacts of the jack 7 and the plug 6, upper alternate contact of relay 22, windings of polarized relay 25, impulse contact of the sending device 20, contact 37 of relay 22, ring contacts of the plug 6 and the jack 7, lower alternate contact of relay 11, lett-hand normal Contact of reversing relay 36, and the left-hand winding of iinpulse responsive relay 35 to battery.

necesa? rlhe opening and closing ot the impulse contact of the sending device 2O during the return movement of the sending device to its normal position causes the opening and closing of the last traced circuit ot the preceding paragraph, whereby impulse responsive relay 35 follows the impulses transmitted by the sending device 20. rThis impulse relay 35 controls the usual motor magnets for the connector switch at theA automatic exchange, whereby connection is established through the switch 38 with telehone line D. After the selecting impulses lia've been transmitted the operator may restore the listening key 5 to normal position. The call bell at the station of telphone line D may be actuated in the usualmanner, and the subscriber in responding to the operation thereof removes the receiver from theswitchhook, causing the energization of reversing relay 36. rllhe energization of this relay 36 reverses the battery connections with the talking conductors oit' the trunk circuit, whereby polarized relay 25 bridged across the talking` conductors ot the link circuit B is energized and opens its contact. rEhe opening of this contact interrupts the locking circuit ot the relay 22, whereupon this relay 22 and pilot relay 23 connected in series therewith are deenergized and restored to normal. rllhe deene-rgization of relay 22 disconnects the sending device 2O from the link circuit B and the deenergization of pilot relay 23 opens the circuit oli and extinguishes the pilot lamp 28.

rll'he deenergization of relay 22 also disconnects the resistance 3() Jfrom parallel relation with the lamp 8 and resistance 1G, whereupon marginal relay 11 releases its armatures reconnecting polarized relay 13 in bridge of the talking conductors and opening the short circuits of the condensers 14 and 15. The direction ot the flow ot' current through the windings of polarized ren lay 13 is now such as to cause the energization ot this relay which, in closing its contact, bridges impedance coil 40 across the talking conductors of the trunk circuit on the manual side or' the condensers. This impedance coil 40r is ot such high impedance that it does not interfere with the talking currents. VUpon the connection ot this impedance coil 40 across the talking conductors, supervisory relay 41 operates over a circuit troni battery through the winding ot' supervisory relay 41, lower normal con tact oiI ringing key 42, lower normal contact ot relay 22, ring contacts of the plug 6 and the jack 7, contact ot' polarized rela;1 13, impedance coil 40, tip contacts of the jack 7 and the plug 6, upper normal contact of relay 22, and upper normal contact of ringing key 42 to ground. The energization of supervisory relay 41 connects resistance 43 in parallel with the lamp 3,

thereby causingthe lamp tobe extinguished,

which indicatesV to the operator that the called subscriber has answered.

Should the operator, prior to the response 'of the party on telephone line D, have needed to use the impulse sending device 20 in connection with another link circuit, the

from the link circuit B which may be done 'by actuating key 26. The opening of the contact of this key 26 interruptslthe lock# ing circuit of relay 22 so that this relay and pilot relay 23 release in the manner before described, to disconnect the sending device 20 from the link circuit and to extinguish the pilot lamp 28. Marginal relay 11 is also deenergized by the deenergization of relay 22. If after the disconnection of the sending device 2O from the link circuit B in the manner just described, the subscriber D responds by removing the receiver from the switchhook, the energizatioii of reversing relay 36 causes the operation .of polarized relay 13. The operation of this relay 13 bridges the impedance coil 40 across the talking conductorsv of the trunk circuit, whereupon supervisory relay 4:1 energizes and extinguishes the lamp 8.

At the conclusion of the conversation, the subscribers restore their receivers to the switchhooks. The restoration of the receiver to the switchhook at the station on telephone line D causes the deenergization of reversing relay 36, whereupon the connection of battery with the talking conductors of the trunk circuit is reversed causing the release of signal-coiitrol polarized relay 13. Impedance coil 40 is removed from bridged relation with the talkingconductors and supervisory relay l1 deenergizes, permitting the lighting of the supervisory lamp 8 which new serves as a disconnect signal to the operator at the manual office. The operator may thereupon disconnect the plug 6 from the jack 7 whereupon all operated apparatus associated with the calling end of the link circuit B and with the trunk circuit C is released and restores to normal position.

lVhat is claimed is:

1. In a telephone exchange system, in combination, a trunk circuit, an operators link circuit connected therewith, a called line, an impulse sending device, means local to the link circuit responsive to the actuation of the impulse sending device for con* necting` it with the link circuit, and means controlled over the trunk circuit by the called line for disconnecting the impulse sending device from the link circuit.

2. In a telephone exchange system, in combination, a trunk circuit, a link circuit conconnected therewith, an impulse sending device, a relay energized inresponse to the actuation of the 'sending device for connecting it 'with the linkcircuit, a locking-ciri cuit forthe relay estab-lished upon the'en ergization thereof for rendering'it's continued energization'independent of the im-4 pulse sending device, .and means controlledv over the trunk circuit for automatically opening said locking circuit.

3. In a telephone exchange system, in com-i bination, a trunk circuit, a'link circuit connected therewith,l` an'impfulse sendingv device, a relay individualto the'l'ink circuit responsive to the "actuation of the impulse sending devicefor cnnectingjnth'e device with` the linkcircuit, and a relayin the link circuit controlled over the'trunk circuit for disconnecting the impulse sending device from the link circuit.

4. Ina telephone exchange system in combination, a trunk circuit, a link circuit connected therewith, an impulse sending device, la relay energized' in response tothe actuation of the sending device for connecting it with-the link circuit, a telephone line,

and a polarized relay controlledvover the trunk circuit and Vby the telephone line for disconnecting the impulse sending device from the linkcircuit. v A

5. In a telephone exchange system,` in

combination, a ltrunk circuitterminating in',`

a jack, Vany operators link circuit terminating in a pluglconnected therewith, an impulse sending.v device, means responsive to the actuation ofthe .impulse-sending. device jfor connecting it with the link circuit, and a signal-control relay controlled'- over 'the trunk circuit for disconnecting the sending device from the link circuit.

G. In al telephone exchangekv system, in

combination, a'trunk circuit, a link circuit` connected therewith, an impulse sendingdevice, a relay energized in response'to an actuation ofthe impulse sendingdevicefor connecting it with' the link circuit, a tele-V phone line, a signal-control relay controlled over the trunk circuit and by the-telephone line for disconnecting the impulse :sending device from thelink circuit, and a super-' visory signal in the link circuit operatingl in response to the energizationof thesignalcontrol relay. A

7. In a telephone exchange"l system, in combination, a trunk circuit, a link circuit connected therewith, an impulse sendingV device, a relay energized-in response to an actuation of the impulse sending device for connecting it the link circuit, a pilot relay, a sending device 'pilot lamp controlled thereby, and Va locking circuitfory the firstmentioned relay established upon the energization thereof and including the windin of the pilot relay. 2

8. In a telephone exchange system, in combination, a trunk circuit terminating in a jack, an cperatorfs link circuit terminating in a plug "connected therewith, an'finipulse' llO CII

sending device, a relay individual to the link circuitresponsive to the actuation of the impulse sending device for connecting it with the link circuit, and operator-controlled means for disconnecting the sending device from the link circuit.

9. ln a telephone exchange system, in combination, a trunk circuit, a link circuit connected therewith, an impulse sending device, a relay energized in response to an actuation ot the impulse sending device for connecting it With the link circuit, a locking circuit i'for the relay established upon the energization thereof iior rendering the :continued energization of the relay independent oi the sending device, and subscriber and operator-controlled means for opening the locking circuit to disconnect the sending device from the link circuit.

l0. In a. telephone exchange system, in combination, a called line, a trunk circuit, a plurality of link circuits, an impulse sending device common to the link circuits, means dependent upon the connection of one or' the link circuits with the trunk circuit, and upon an actuation oix the impulse sending device for rendering the sending device individual to the engaged link circuit, and means controlled by the called line over the trunk circuit for disconnecting the impulse sending device from the link circuit.

11. In a telephone exchange system, in combination, a trunk circuit comprising a talking conductor, a condenser in the talking conductor, a link circuit connected With the trunk circuit, an impulse sending device, means responsive to an actuation of the im pulse sending device for connecting it with the link circuit and for establishing a direct current path around the condenser, and an impulse relay controlled by the impulse sending device over a circuit including the direct current path around the condenser.

12. In a telephone exchange system, in combination, a trunk circuit comprising a talking conductor, a condenser in the talking conductor, a link circuit connected With the trunk circuit, an impulse sending device, a relayenergized in response. to an actuation of the impulse sending device for connecting it With the link circuit, a second relay operating in response to the energization of the iirst relay for establishing direct current path around the condenser, and an impulse relay controlled by the impulse sending device over a circuit including the direct current path around the condenser.

13. ln a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors, a condenser connected in one of the talking conductors, a signal-control relay bridged across the talking conductors, a link circuit connected With the trunk circuit, an impulse sending device, means responsive to an actuation of incase? the impulse sending device for connecting it with the link circuit and for short-circuiting the condenser and opening the bridge including the signal-control relay.

lll. ln a telephone eXchange system, a trunk circuit, automatic switches accessible thereto, a called line, an operators cord circuit connected With said trunk circuit, an impulse sending device having a forward and backward movement, a relay in the cord circuit responsive to the initial forward movement of the impulse sending device lor connecting said device VWith the cord circuit, means controlled by the backward movement of said device to set said switches, and means controlled by the operator and the called line for disconnecting said device from said cord circuit.

15. In a telephone exchange system, a trunk circuit, a plurality ot cord circuits, an impulse sending device common to the cord circuits, means responsive to the connection of one of the cord circuits with the trunk circuit and the initial actuation of the impulse sending device for connecting said de-.v

vice to the engaged cord circuit, and a polarized relay common to the cord circuits controlled over the trunk circuit for disconnecting said device Yfrom said cord circuit.

16. ln a telephone exchange system, a trunk circuit, a plurality of cord circuits, an impulse sending device common to the cord circuits, a rela-y for each of said cord circuits, circuit local to the cord circuit completed upon the initial actuation oi said device for said relay to connect said device to said cord circuit, and a second relay common to said cord circuits controlled over the trunk circuits tor disconnecting said device from said cord circuit.

1'4". ln a telephone exchange system, a trunk circuit comprising a pair of talking conductors, a condenser in each of the talking conductors, a cord circuit connected with the trunk circuit, an impulse sender, means for connecting the sender to the cord circuit, a relay in the trunk circuit operating in response to the actuation of said connecting means for establishing a direct current path around each of the condensers, and means controlled by the operator for removing the direct current path around the condensers.

18. ln a telephone exchange system, an inductively continuous trunk circuit, a cord circuit connected thereto, an impulse sender associated with the cord circuit, and operator controlled means for connecting the sender to the cord circuit and for rendering the trunk circuit conductively continuous.

19. ln a telephone exchange system, an inductively continuous trunk circuit, a cord circuit connectedthereto, an impulse sender, means for connecting the sender to the cord lltl circuit and for rendering said trunk circuit conductively continuous, an impulse relay, and an impulse sending circuit, including two conductors ot' said trunk circuits in series and said sender, for controlling said relay.

20. In a telephone exchange system, a trunk circuit comprising a pair of talking conductors, a source of current connected thereto, a cord circuit connected to said trunk circuit, a source of current connected to said cord circuit, condenser-s in said trunk circuit for separating said sources, an impulse sender on one side of'said condensers and an impulse relay on the other side of said condensers, and a switch associated With said cord circuit for connecting said sender to said trunk circuit and for short-circuiting said cendensers to place said relay under control of said sender.

2l. In a telephone exchange system, a

trunk circuit comprising a pair of talking conductors, an impulse relay connected to one end of said trunk circuit, a cord circuit connected to the other end of said trunk circuit, condensers in said trunk circuit, an impulse relay, an impulse sender associated with said cord circuit, and means controlled by the operator for connecting said sender to said cord circuit and for short-circuiting said condensers to connect said sender in series relationship With said relay.

22. In a telephone exchange system, a trunk circuit comprising a pair of talking conductors, a condenser in each of the talking conductors, a cord circuit connected With the trunk circuit, an impulse sender, means for connecting the sender to the cord circuit, means in the trunk circuit operating in response to the actuation of said sender connecting means Jfor establishing a direct current path around each of the condensers, and an impulse relay controlled by the sender over a circuit including the direct current path around the condensers.

23. In a telephone exchange system, a calling station, a trunk circuit comprising a pair of talking conductors for extending a connection therefrom, a condenser in each of said conductors, a relay, contacts thereon for establishing a by-path around said condensers, and manual controlling means at the calling station for actuating said relay.

In testimony whereof, I have signed my name to this specification this 28th day of July, 1919.

HENRY L. HOFFMANN. 

